1. Field of the Invention
The present invention relates to a process for disposing raw concrete sludge, an apparatus for disposing such sludge, and an apparatus for forming aggregate from such sludge. More particularly, the invention relates to a process for disposing raw concrete sludge whereby aggregate is separated from, what is called, "residual raw concrete" remaining in a concrete mixing truck from which a predetermined amount of raw concrete has been discharged for use, and waste water resulting from washing the mixing truck (such residual raw concrete and waste water are hereinafter referred to as "the sludge" in this invention), and the sludge which has thus been separated from the aggregate is disposed. The invention also relates to an apparatus for obtaining the aggregate from the resultant sludge.
2. Description of Related Art
Conventionally, a chemical admixture (hereinafter simply referred to as "the admixture") is used for raw concrete to improve its quality. The admixture is one type of surfactant which acts to reduce the amount of water and to circulate together with air. Such an admixture can be divided into two types. One type of admixture acts to allow cement particles to be dispersed in water so as to improve hydration effects, thereby promoting the solidification of cement. The other type of admixture acts to be adsorbed to the cement particles so as to prevent the initial stage of hydration, thereby delaying the solidification of cement.
Immediately after being generated, the sludge, such as the residual raw concrete, is often affected by such an admixture so that the cement particles are dispersed in water so as to be emulsified. Accordingly, when such sludge is dehydrated on the same day, the filter cloth used during dehydration is likely to be quickly clogged with the cement particles, thus significantly hampering dehydrating characteristics. In order to avoid such a problem, the sludge is generally left in an agitation storage vessel (not shown) for approximately ten hours and is then dehydrated the following day. However, if dehydration is performed after a lapse of many hours, the hydration reaction of the cement has gone far ahead, thus deteriorating the agglomeration force of the cement particles. The resultant cement is soft and difficult to handle, thus causing pollution if it is set aside.
As described above, the dehydrated cake which has undergone dehydration the following day exhibits in a weak agglomeration force. Since no development has been made for measures for recycling such dehydrated cakes, there is no choice but to dispose them as restricted industrial waste. However, it is difficult to ensure a disposal site, and the cost of disposal is consequently very high. In order to solve the above problems, a dehydration process should be performed before the cement loses its agglomeration force immediately after the sludge is generated, thus obtaining the resultant hard cake, which can be recycled, thereby saving a large amount of cost.
However, even though the above problem is overcome to obtain the hard cake of high strength, such cakes are deposited in a conventional manner so as to result in a massive rock-like shape, which is time-consuming and requires great efforts to destroy.
Further, the direct and immediate processing of the dehydrated cake without being cured produces a strong adhesion of the cement water to the apparatus, which leads to the malfunctioning of the apparatus. Thus, it is difficult to put the foregoing process for disposing raw concrete sludge into practical use.